The KEY: The Other Side of Unintended Consequences

What is the other side of unintended consequences?
Here is how Rafael puts it. The Vietnam War was terrible. We lost many lives. But very few people know that many thousands of people are saved each year because of what we learned in Vietnam. Emergency medicine was transformed as a result of the harsh learning laboratory of Vietnam.

What are your positive and surprising unintended consequences? What challenges and setbacks have you grappled with that can help you reinvent how you do things?